1. Field of the Invention
The present invention relates to an azo compound used as an organic photoconductive material, and to a method of preparing the azo compound.
2. Discussion of the Related Art
Conventionally, an azo compound has been used as an organic photoconductive material, particularly as a charge generation pigment in a multilayered photoreceptor being an embodiment of electrophotographic photoreceptors.
The multilayered photoreceptor is known to be a photoreceptor including an electroconductive substrate; a charge generation layer formed on the electroconductive substrate, including a charge generation pigment having charge generatability as a main component; and a charge transport layer formed on the charge generation layer, efficiently absorbing a charge generated by the charge generation layer and including a charge transport material capable of transporting the charge as a main component. Conventionally, as azo compounds for use in such photoreceptors, Japanese published unexamined applications Nos. 47-37543 and 52-55643 disclose benzidine bisazo compounds; Japanese published unexamined application No. 52-8832 discloses stilbene bisazo compounds; Japanese published unexamined application No. 58-222152 discloses diphenylhexatriene bisazo compounds; and Japanese published unexamined application No. 58-222153 discloses diphenylbutadiene bisazo compounds.
However, the multilayered photoreceptor using a conventional azo compound typically has low sensitivity, which is unsatisfactory to a photoreceptor for high-speed copiers. One of the reasons is thought that impurities are not fully removed from the azo compound because the azo compound typically has very low solubility with an organic solvent and is purified only by being washed with an organic solvent. In addition, a combination with a long-time dispersion process by methods such as a ball milling method to prepare a dispersion liquid in which microscopic particles are uniformly dispersed or a use of a resin dispersion stabilizer is inevitable.
Because of these reasons, a need exists for an azo compound useful as an organic photoconductive material, overcoming the conventional drawbacks.